I think it's at least as safe as normal NIP-46 remote signing *if* you yourself retain a shard of the key under your exclusive control (and require *all* shards for a signature).
If you don't retain a shard, it seems conceivable that your friends may have worse security practices than you yourself would have had, and that they could all be vulnerable to the same type of attack.
So I guess I'd use the method as long as I myself keep exclusive control over a sufficient number of shards to give me a veto.🤷♂
